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Java > Open Source Codes > javax > servlet > jsp > tagext > TryCatchFinally


1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18  
19 package javax.servlet.jsp.tagext;
20
21
22
23 /**
24  * The auxiliary interface of a Tag, IterationTag or BodyTag tag
25  * handler that wants additional hooks for managing resources.
26  *
27  * <p>This interface provides two new methods: doCatch(Throwable)
28  * and doFinally(). The prototypical invocation is as follows:
29  *
30  * <pre>
31  * h = get a Tag(); // get a tag handler, perhaps from pool
32  *
33  * h.setPageContext(pc); // initialize as desired
34  * h.setParent(null);
35  * h.setFoo("foo");
36  *
37  * // tag invocation protocol; see Tag.java
38  * try {
39  * doStartTag()...
40  * ....
41  * doEndTag()...
42  * } catch (Throwable t) {
43  * // react to exceptional condition
44  * h.doCatch(t);
45  * } finally {
46  * // restore data invariants and release per-invocation resources
47  * h.doFinally();
48  * }
49  *
50  * ... other invocations perhaps with some new setters
51  * ...
52  * h.release(); // release long-term resources
53  * </pre>
54  */
55
56 public interface TryCatchFinally {
57
58     /**
59      * Invoked if a Throwable occurs while evaluating the BODY
60      * inside a tag or in any of the following methods:
61      * Tag.doStartTag(), Tag.doEndTag(),
62      * IterationTag.doAfterBody() and BodyTag.doInitBody().
63      *
64      * <p>This method is not invoked if the Throwable occurs during
65      * one of the setter methods.
66      *
67      * <p>This method may throw an exception (the same or a new one)
68      * that will be propagated further up the nest chain. If an exception
69      * is thrown, doFinally() will be invoked.
70      *
71      * <p>This method is intended to be used to respond to an exceptional
72      * condition.
73      *
74      * @param t The throwable exception navigating through this tag.
75      * @throws Throwable if the exception is to be rethrown further up
76      * the nest chain.
77      */
78  
79     void doCatch(Throwable JavaDoc t) throws Throwable JavaDoc;
80
81     /**
82      * Invoked in all cases after doEndTag() for any class implementing
83      * Tag, IterationTag or BodyTag. This method is invoked even if
84      * an exception has occurred in the BODY of the tag,
85      * or in any of the following methods:
86      * Tag.doStartTag(), Tag.doEndTag(),
87      * IterationTag.doAfterBody() and BodyTag.doInitBody().
88      *
89      * <p>This method is not invoked if the Throwable occurs during
90      * one of the setter methods.
91      *
92      * <p>This method should not throw an Exception.
93      *
94      * <p>This method is intended to maintain per-invocation data
95      * integrity and resource management actions.
96      */
97
98     void doFinally();
99 }
100
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